Horizon Storms — Kevin J. Anderson

Caught in the middle of a titanic struggle between two alien superpowers, the factions of humanity and their allies, the Ildirans, are under siege. Can they resolve their differences to fight a common threat? For the leader of the Roamers, survival means extending a helping hand to others, while the chairman of the Terran Hansa plans to use a new, untested alien weapon regardless of the consequences. And for the new Ildiran MageImperator, survival involves throwing off the choking traditions of the Empire--even if it might trigger a civil war. As old intrigues and dark secrets come to light, a man who is believed to be long dead returns with an ally who may save mankind. But this new fragile hope will be threatened by a fresh betrayal--the most bitter and brutal of them all...